This invention relates to a driving method for a three-phase stepping motor.
In recent years, stepping motors have found increasing applications in automobiles. The requirements for the stepping motors for automotive use are size reduction, higher torque, and low vibration.
Description will first be made of the driving method of the conventional three-phase stepping motor. FIG. 9 is a timing chart showing currents of the respective coils by the driving method of the conventional three-phase stepping motor. Reference numeral 21 denotes a current flowing through a first coil, 22 a current flowing through a second coil, and 23 a current flowing through a third coil. FIG. 10 is a conceptual diagram for explaining FIG. 9. Reference numeral 24 denotes a first terminal of a coil, 25 a second terminal of the coil, and 26 a third terminal of the coil.
Description will next be made of the driving method of the thus constructed three-phase stepping motor referring to its operation. First of all, a current is conducted from the first terminal to the second terminal. Next, a current is conducted from the third terminal to the second terminal. Subsequently, a current is conducted according to the sequence shown in the conceptual diagram. According to this power conduction method, the stepping motor rotates in units of basic step angles.
However, in the above-mentioned conventional construction, a vibration peculiar to the stepping motor is determined by the design of the stator and the rotor, which constitute the stepping motor. The conventional stepping motor has a problem that this vibration is attributable to the influence of machining accuracy, and therefore, the stepping motor cannot be used in electric equipment which is required to have low vibration.